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BISHOP SCOTT BOYS’ SCHOOL (Affiliated to CBSE, New Delhi) Affiliation No.: 330726, School Campus: Chainpur, Jaganpura,
By-Pass, Patna 804453. Phone Number: 7061717782, 9798903550. , Web: www.bishopscottboysschool.com Email: [email protected]
STUDY COURSE MATERIAL
CHEMISTRY SESSION-2020-21
CLASS-X
TOPIC: CHEMICAL REACTIONS AND EQUATION
DAY-1
TEACHING MATERIAL
Chemical Reaction A chemical reaction is the process of breaking the chemical bonds of the reacting substances and making new bonds to form new products.
A chemical bond is the force that holds the atoms of a molecule together, as in a compound.
A chemical reaction occurs when particles collide. Eg: H2 + Cl2 ----> 2HCl
Characteristics of Chemical reactions Certain chemical reactions are characterized by changes that are quite easily observed. Evolution of gas: In many chemical reactions, one of the product is gas. Example: When zinc reacts with dilute sulphuric acid hydrogen gas is evolved, with effervescence. Zn + H2SO4 -----> ZnSO4 + H2 Note: The formation of gas bubbles in a liquid during a reaction is called effervescence. Change of colour: Certain chemical reactions are characterized by change in colour of reactants Example: Fe + CuSO4 ----> FeSO4 + Cu [Iron] [ blue solution ] [ green solution ] [ red deposit ] Formation of precipitates: Some chemical reactions are characterized by the formation of precipitate. Example: AgNO3 + NaCl ----> AgCl + NaNO3 [ white ppt ] Change of state: In many chemical reactions, a change of state is observed. Example: NH3 (g) + HCl (g) ⇌ NH4Cl (s)
Chemical Equation A chemical equation is the symbolic representation of a chemical reaction using the symbols and formulae of the substances involved in the reaction. The reaction can be represented by either a word equation or a chemical equation.
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Word equation: Carbon + Oxygen ⟶ Carbon dioxide Chemical equation C + O2 ⟶ CO2
Steps involved in writing a chemical equation: 1. Write the symbols or the formulae of the reactants on the left side with a (+) sign
between them. 2. Write the symbols or the formulae of the products on the right side with a (+) sign
between them. 3. Put the sign of an arrow (⟶) in between the reactant side and the product side. 4. Represent the reactants and the products in their molecular forms.
Skeleton equation It is defined as an equation that represents a chemical reaction but is unbalanced i.e. the total number of atoms of each element on the two sides are not equal. Example: KNO3 -----------> KNO2 + O2
Balanced equation It is an equation in which the total number of atoms of each element in the reactants, on the left side of equation is same as the number of atoms in the products formed, on the right side of equation. Example: 2 KNO3 ------------> 2 KNO2 + O2 An equation must be balanced in order to comply with the “Law of conservation of mass”. Balancing the chemical equation by hit and trial method Count the number of times an element occurs on either side and note down in following format.
Elements
Number of atoms
Reactants Products
Now balance the elements having maximum number of occurrence or non-metal by multiplying with natural number.
Note: The multiplicative number should always note down as co-efficient.
When the number of atoms in both the reactant and product side are equal then note down the balanced chemical equation. Example: Balance the chemical equation - Pb(NO3)2 --------------> PbO + NO2 + O2
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Elements
Number of atoms
Reactants Products
Pb
1 x 2 1 x 2
N
2 x 2 1 x 4
O
6 x 2 1 x 2 + 2 x 4 + 2
Hence balanced chemical equation is 2Pb(NO3)2 -----------------> 2PbO + 4NO2 + O2
VIDEO-LINKS
LINK-1
https://www.khanacademy.org/science/biology/chemistry--of-life/chemical-bonds-and-
reactions/v/chemical-reactions-introduction
LINK-2
https://www.youtube.com/watch?v=8w9yRxBZzSo
LINK-2
https://www.youtube.com/watch?v=zmdxMlb88Fs
ASSIGNMENT
Fill in the blanks:-
1.Addition of hydrogen in a substance in a reaction is known as___________ reaction. 2.In a ________ reaction two or more substances combine to form a new single substance. 3.Unbalanced reactions are also known as _________
Question 4.Balance the following chemical equitations:-
a)HNO3 + Ca(OH)2 -> Ca (NO3)2 + H2O b)NaOH + H2SO4 -> Na2SO4 + H2O c)NaCI + AgNO3 -> AgCI + NaNO3 d)BaCI2 + H2SO4 -> BaSO4 + HCI
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DAY-2
TEACHING MATERIAL
Types of chemical reaction
1. Combination reaction
2. Decomposition reaction
3. Displacement reaction
4. Double displacement reaction
5. Double decomposition
6. Oxidation and reaction
Combination reaction A reaction in which two or more substances combined together to form a single substance is called a combination reaction. A + B ---------------> AB
In combination reactions:
(i) Two elements combine to form a compound
Example: C + O2 -------------> CO2 2Fe + 3Cl2 -----------> 2FeCl3
(ii) An element and a compound combine to give a new compound
Example: 2CO + O2 -----------> 2CO2 2SO2 + O2 ------------> 2SO3
(iii) Two or more compounds combine to form a single product.
Example: NH3 + HCl ---------------> NH4Cl
Decomposition reaction It is the breaking up of a compound either into elements or simpler compounds, such
that these products do not recombine to form the original compound.
It may occur in the presence of heat, light or by passage of an electric current.
It is of three types
(i) Thermal decomposition reaction: A decomposition reaction that is brought
about by heat is known as thermal decomposition reaction.
Examples: 2KNO3 ---------------> 2KNO2 + O2 CaCO3 ----------> CaO + CO2
(ii) Electrolytic decomposition: A decomposition reaction that is brought about by
electric current is known as electrolytic decomposition.
Examples: 2H2O --------------> 2H2 + O2 2NaCl --------------> 2Na + Cl2
(iii) Photolytic decomposition: A decomposition reaction that is brought by
light energy is known as photolytic decomposition.
Examples: 2AgNO3 -------------> 2Ag + 2NO2 + O2 2H2O2 --------------> 2H2O + O2
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Displacement reaction A chemical reaction in which a high reactive element displaces low reactive element from its salt solution is called displacement reaction. Example: Zn + CuSO4 -----------> ZnSO4 + Cu
It is of two types.
(i) Cation displacement reaction: A reaction in which high reactive metal displaces
low reactive metal from its salt solution.
Example: 2Na + ZnSO4 ---------------> Na2SO4 + Zn
(ii) Anion displacement reaction: A reaction in which high reactive anion (non-
metal) displaces less reactive anion from its solution.
Example: 2KI + Cl2 -------------> 2KCl + I2
Double displacement reaction A chemical reaction in which two compounds in a solution react to form two new compounds by mutual exchange of radicals is called double displacement reaction. AB + CD ----------------> AD + CB
It is of two types.
(i) Precipitation reaction: A chemical reaction in which two compounds in their
aqueous state react to form an insoluble salt as one of the products is known as a
precipitation reaction.
Example: BaCl2 + Na2SO4 -----------------> BaSO4 + 2NaCl [White ppt]
(ii) Neutralization reaction: The reaction between an acid and a base that forms salt
and water only is referred as a neutralization reaction.
Example: NaOH + HCl ---------------> NaCl + H2O
Exothermic reaction A chemical reaction in which heat is given out is called exothermic reaction. Example: CH4 + 2O2 --------------> CO2 + Heat
Endothermic reaction A chemical reaction in which heat is absorbed is called endothermic reaction. Example: N2 + O2 --------------------> 2NO
Oxidation Oxidation is defined as a chemical process that involves:
Addition of oxygen
C + O2 --------------> CO2 Addition of electronegative ion
2FeCl2 + Cl2 ----------> 2FeCl3 Removal of hydrogen
H2s + Cl2 --------> 2HCl + S Removal of electropositive ion
2KI + H2O2 -----------> 2KOH + I2
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Reduction
Reduction is defined as a chemical process that involves: Removal of oxygen
CuO + H2 ---------> Cu + H2O Removal of electronegative ion
2FeCl3 + H2S ------------> 2FeCl2 + 2HCl + S
Addition of hydrogen
Cl2 + H2S --------------> 2HCl + S Addition of electropositive ion
2HgCl2 + SnCl2 -----------------> Hg2Cl2 + SnCl4
Redox reaction A reaction in which oxidation and reduction take place simultaneously is known as redox reaction.
Rancidity
Rancidity is the complete or incomplete oxidation of fats and oils when exposed to air, light or moisture.
It can be prevented using the following methods:
(i) Adding antioxidants to food
(ii) Storing food in air-tight containers
(iii) Refrigerating food
(iv) Replacing oxygen in the container with another gas.
VIDEO-LINKS
LINK 1:
https://www.youtube.com/watch?v=HmNsQKLRgh8
LINK 2:
https://www.youtube.com/watch?v=HeKq9V54xlM
LINK 3:
https://www.youtube.com/watch?v=gWPjVF3WFzU
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LAB ACTIVITY
1) https://www.youtube.com/watch?v=eLkGX2jAKoM
2) https://www.youtube.com/watch?v=lDas5ekKT94
ASSIGNMENT
https://physicscatalyst.com/Class10/chemical-reactions-and-equations-class-10-
test.php
https://www.learncbse.in/ncert-solutions-class-10-science-chapter-1/
LAB MANUAL
http://ncert.nic.in/ncerts/l/jelm102.pdf
https://www.cbsetuts.com/ncert-class-10-science-lab-manual-types-reactions/
CONCEPT MAP
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DAY-3
TEACHING MATERIAL : - ACID AND BASES
ACIDS Acids are defined as compounds which contain one or more hydrogen atom and when dissolved in water, they produce hydronium ions (H3O+).
The word ‘acid’ comes from the Latin word acidus, meaning ‘sour’.
Note: (i) At first, the acid molecule furnishes hydrogen ion i.e., H+ ion in aqueous solution. But this H+ ion cannot exist independently. Therefore, it combines with a water molecule to form hydronium ion. (ii) Hydrogen is common in all acids. Examples: Hydrochloric acid, Sulphuric acid, Nitric acid, etc. HCl + H2O ⇌ H3O+ + Cl- H2SO4 + H2O ⇌ 2H3O+ + SO42-
The hydrated hydrogen ion that exists in the solution of acids is called a hydronium ion. H+ + H2O ⟶ H3O
CLASSIFICATION OF ACIDS
Acids can be classified in following ways. 1. Depending on their sources
(a) Organic acids: Acids which are obtained usually from plants are called organic acids. They contain carbon. Examples: Oxalic acid (COOH)2 , Acetic acid (CH3COOH)
(b) Inorganic acids: Acids which are obtained usually from minerals are called inorganic acids. They do not contain carbon (except carbonic acid H2CO3). Examples: Hydrochloric acids (HCl), Sulphuric acids (H2SO4), Nitric acid (HNO3), etc.
2. Depending on their strength
Strength of an acid depends on the degree of ionization and concentration of hydronium ions produced by that acid in aqueous solution.
(a) Strong acids: Acids which vigorously ionizes in aqueous solution and produce high concentration of hydronium ions are called strong acids. Examples: All mineral acids (except carbonic acid)
(b) Weak acids: Acids which ionizes partially in aqueous solution and produce less concentration of hydronium ions are called weak acids. Examples: All organic acids, Carbonic acids.
Note:
1. Degree of ionization = 𝑁𝑜.𝑜𝑓 𝑎𝑐𝑖𝑑 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒𝑠 𝑖𝑜𝑛𝑖𝑠𝑒𝑑
𝑡𝑜𝑡𝑎𝑙 𝑛𝑜.𝑜𝑓 𝑎𝑐𝑖𝑑𝑠 𝑝𝑟𝑒𝑠𝑒𝑛𝑡 𝑖𝑛 𝑎𝑞𝑢𝑒𝑜𝑢𝑠 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 x 100
2. If the degree of ionization for an acid, bases or salt in aqueous solution is
greater than 30%, it is strong and if less than 30%, it is weak.
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3. Depending on their concentration
Concentration of an acid means the amount of acid present in a definite amount of its aqueous solution.
(a) Concentrated acid: An acid which contains a very small amount of water or no water is
called concentrated acid.
(b) Dilute acid: An acid which contains far more amount of water than its own mass is known as dilute acid.
Note: (i) In order to dilute an acid, pour acid into water in small amounts and stir constantly. (ii) Water is not added to acid as it is an exothermic process.
4. Depending on molecular composition
(a) Oxy-acids: Those acids which contain oxygen along with hydrogen and some other
element.
Examples: Nitric acid, Sulphuric acid, Phosphoric acid, etc.
(b) Hydracids: Those acids which contain hydrogen and a non-metallic element, and no
oxygen.
Examples: Hydrochloric acid (HCl), Hydro bromic acid (HBr), Hydro iodic acid (HI)
5. Depending on their basicity
The basicity of an acid is defined as the number of hydronium ions that can be produced by the ionization of one molecule of that acid in aqueous solution.
(a) Monobasic acids: Acids which on ionization in water produce one hydronium ion per
molecule of the acid.
Example: Hydrochloric acid, Nitric acid, Hydro bromic acid, etc. These acids have one replaceable hydrogen ion, so they ionize in one step.
HCl + H2O ⟶ H3O+ + Cl-
(b) Dibasic acids: Acids which on ionization in water produce two hydronium ions
per molecule of the acid. Examples: Sulphuric acid (H2SO4), Oxalic acid (H2C2O4), Sulphurous acid (H2SO3), etc.
These acids have two replaceable hydrogen ions, so they ionize in two steps.
H2SO4 + H2O ⇌ H3O+ + HSO4- HSO4- + H2O ⇌ H3O+ + SO42-
(c) Tribasic acids: Acids which on ionization in water produce three hydronium
ions per molecule of the acid.
Examples: Phosphoric acid (H3PO4), Phosphorous acid (H3PO3) These acids have three replaceable hydrogen ions, so they ionize in three steps.
H3PO4 + H2O ⇌ H3O+ + H2PO4- H2PO4- + H2O ⇌ H3O+ + HPO42- HPO42- + H2O ⇌ H3O+ + PO43-
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VIDEO-LINKS
LINK 1: https://www.youtube.com/watch?v=B5AZxV2-Sv0
LINK 2: https://www.youtube.com/watch?v=DwJ7L6R0tLQ
ASSIGNMENT
1. Which one of the following is acidic? (a) Lemon juice (b) Tomatoes (c) Milk (d) All 2. Which one of the following will turn red litmus blue? (a) Vinegar (b) Baking soda solution (c) Lemon juice (d) Soft drinks 3. Which one of the following will turn blue litmus red? (a) Vinegar (b) Lime water (c) Baking soda solution (d) Washing soda solution
DAY-4
TEACHING MATERIAL : - PROPERTIES OF ACIDS
Physical properties (i) Taste: Acids have a sour taste.
(ii) Physical State: Some acids are solid and some are liquid at room temperature.
Examples:
Acids Formula State
Boric acid H3BO3
Solid Acids Oxalic acid (COOH)2
Tartaric acid C4H6O6
Citric acid C6H8O6
Phosphoric acid H3PO4
Acetic acid CH3COOH Liquid Acids
Formic acid HCOOH
(iii) Effect on skin: All strong mineral acids have corrosive action on the skin and cause painful
burns.
(iv) They change the colour of indicators.
Indicators Colour change in acidic medium
Litmus Blue to red
Methyl orange Orange to pink
Phenolphthalein Remains colourless
(v) They are strong electrolytes.
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Chemical properties (i) Reaction with active metals: Metals react with acid to form metallic salt and hydrogen.
Active metal + Acid ⟶ Salt + Hydrogen Mg + 2HCl ⟶ MgCl2 + H2 ↑ Zn + 2HCl ⟶ ZnCl2 + H2 ↑
(ii) Reaction with bases: Acids neutralize bases to form salt and water only.
CuO + H2SO4 ⟶ CuSO4 + H2O NaOH + HNO3 ⟶ NaNO3 + H2O
(iii) Reaction with carbonates and bicarbonates: Acids liberate carbon dioxide on reaction
with metallic carbonates and bicarbonates.
CaCO3 + 2HCl ⟶ CaCl2 + H2O + CO2 ↑ Ca(HCO3)2 + 2HCl ⟶ CaCl2 + 2H2O + 2CO2 ↑
(iv) Reaction with sulphites and bisulphites: Acids react with sulphites and bisulphites
of metals to liberate sulphur dioxide.
CaSO3 + 2HCl ⟶ CaCl2 + H2O + SO2 ↑ NaHSO3 + HCl ⟶ NaCl + H2O + SO2 ↑
(v) Reaction with sulphides: Acids react with metal sulphides to liberate hydrogen sulphide.
ZnS + 2HCl ⟶ ZnCl2 + H2S ↑ FeS + H2SO4 ⟶ FeSO4 + H2S ↑
VIDEO-LINKS LINK 1: https://www.youtube.com/watch?v=9P-qsbmIrz4
LINK 2: https://www.youtube.com/watch?v=NLJvrvyeV0Q
LINK 3: https://www.youtube.com/watch?v=Isrhnyglqf0
ASSIGNMENT 1) Take few samples of acidic solution used in your daily life and classify them according to
their sources.
2) Why does lemon juice changes the color of floor when poured?
DAY-5
TEACHING MATERIAL : -
BASES: A base is either metallic oxide or a metallic hydroxide or aqueous ammonia which reacts with hydronium ions of an acid to form salt and water only.
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Examples: CuO + 2HCl ⟶ CuCl2 + H2O Mg(OH)2 + H2SO4 ⟶ MgSO4 + 2H2O
They contain either displaceable oxide (O2-) or displaceable hydroxide ion (OH-).
Alkalis An alkali is a basic hydroxide which when dissolved in water produces hydroxyl (OH-) ions as the only negatively charged ions.
All alkali is a base soluble in water
Examples: Sodium Hydroxide (NaOH, Caustic soda), Potassium hydroxide (KOH, caustic potash), Calcium hydroxide [Ca(OH)2, slaked lime], etc. Note: All alkalis are bases but all bases are not alkalis. Examples: Ferric hydroxide [ Fe(OH)3], cupric hydroxide [ Cu(OH)2]
CLASSIFICATION OF BASES
1. On the basis of their strength
(a) Strong base: It undergoes almost complete ionization in aqueous solution and
produce high concentration of OH-.
Examples: NaOH, KOH etc.
(b) Weak base: It undergoes only partial ionization in aqueous solution to produce a
low concentration of OH-.
Examples: NH4OH, Ca(OH)2
2. On the basis of their acidity
The number of hydroxyl ions [OH]- which can be produced per molecule of the base in aqueous solution.
(a) Monoacidic base: It is a base that dissociates in aqueous solution to produce one
OH- ion per molecule of that base.
Examples: NaOH, KOH and NH4OH
(b) Diacidic base: It is a base that dissociates in aqueous solution to produce two OH-
ion per molecule of that base.
Examples: Ca(OH)2 and Cu(OH)2
(c) Triacidic base: It is a base that dissociates in aqueous solution to produce three
OH- ion per molecule of that base.
Examples: Al(OH)3 and Fe(OH)3
Properties of bases
Physical properties 1. They have a sharp and bitter taste.
2. They change the colour of indicators.
Indicators Colour change in acidic medium
Litmus Red to blue
Methyl orange Orange to yellow
Phenolphthalein Colourless to pink
3. They are soapy substances, i.e., they are slippery to touch.
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4. They are strong electrolytes.
5. They show a mild corrosive action (slight burn) on the skin.
Chemical properties 1. Strong alkalis absorb carbon dioxide from the air to form carbonates.
Examples: 2NaOH + CO2 ⟶ Na2CO3 + H2O 2KOH + CO2 ⟶ K2CO3 + H2O
2. They neutralize acids to form salt and water.
Examples: Ca(OH)2 + 2HCl ⟶ CaCl2 + 2H2O Fe(OH)2 + 2HCl ⟶ FeCl2 + 2H2O
3. When they are warmed with an ammonium salt, ammonia gas is given out.
Example: NH4Cl + NaOH ⟶ NaCl + H2O + NH3↑ 4. They precipitate as insoluble metallic hydroxides when added to the solutions of the
salts of heavy metals like copper, iron, zinc, etc.
Example: CuSO4 + 2NH4OH ⟶ (NH4)2SO4 + Cu(OH)2↓ (Pale blue)
VIDEO-LINKS
LINK 1: https://www.youtube.com/watch?v=zH-u2OzXPZE
LINK 2: https://www.youtube.com/watch?v=tDffmdkbXv0
LAB ACTIVITY
https://www.youtube.com/watch?v=5Gov3XUXJHE
https://www.youtube.com/watch?v=FCNYhFyhk3U
https://www.youtube.com/watch?v=DZY_28kLgY0
LAB MANUAL
https://www.cbsesamplepapers.info/cbse/cbse-class-10-science-practical-skills-
properties-of-acids-and-bases
ASSIGNMENT
1. Differentiate between the chemical properties of acid and base.
2. Write down the bases used in our daily life . Also mention their types.
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CONCEPT MAP